yeesh, this took a hot minute, but I adore how it came out so it's all okay :)
anyway, into the details

Sea Lavender [pictured left] is the daughter of Sunshine Spectacle, and the unknowing half-sister of Trixie Lulamoon. Lavender never knew her father, and was raised exclusively by Sunshine as a matched set of poor drifters. She did not have the best life under her mother's care (though it's possible she could've had an even worse one under her father's), but she did have her mother's unconditional love and affection.. at least, for a time. The two are incredibly close throughout Lavender's early childhood; she refuses to leave her mother's side, and at first, Sunshine wouldn't have it any other way. But over time, Sunshine grows distant.. playing at motherhood was fun for awhile, but it's really starting to be a commitment. The little filly is eating up all of her funds, and she can't go anywhere without the little tyke clinging to her ankles (she doesn't exactly have friends that can watch her kid for a night). Heck, she hadn't even named the damned thing yet, she'd just been calling her variations on "kid" and "runt" in the hopes that she'd come up with something in the meantime.

Sunshine considers her options carefully. It's clear; there is no way to live her life like she used to with the little bugger around. She can't exactly just drop the kid off with her father (even if she knew where the stallion was, he had already rejected her once), and leaving her in the middle of nowhere to fend for herself was a no-go (what, even if if she didn't want the kid herself, she didn't want her to die).. she mulls it over for awhile before the perfect opportunity presents itself.

Sunshine ends up in a sleepy town on the coastal outskirts of Vanhoover, and she meets a kindly older mare who offers to look after Lavender while her mother goes to the town's market after noticing that Sunshine looked incredibly stressed. Sunshine jumps at the chance for a brief respite, telling Lavender that she'll be right back.. and after that, Lavender never sees her mother again. The older mare, Dovekie Song, dutifully watches after the filly for the afternoon while waiting for the other mare to get back.. and waiting, and waiting, and waiting.. it became clear enough to Dove that Sunshine would not be returning. She's at a bit of a loss for what to do, but knows she can't just abandon the filly here.

She offers the kid a warm meal back at her home, and though she's resistant to the idea and doesn't want to leave their spot for fear that her mother won't be able to find her, eventually the empty feeling in her gut convinces her. She hasn't had a good meal.. well, ever, really. The pair head back to Dove's house, where Lavender barrels straight into Dove's wife, Seashore Mallow, as she's outside tending to her garden. Mallow helps calm the little filly alongside her wife, and Dove quietly explains the situation after telling Lavender to head inside. The two share their concerns and ponder over what to do, before eventually heading inside to start on Lavender's promised dinner.

The two mares ask the filly a variety of questions over dinner, trying to learn if she has any family anywhere that might be missing her, or how she even ended up traveling with that mare in the first place (was that even her mother to begin with..?). Through their questioning, they learn that the little filly's mother never gave her a name, that she's been traveling alongside her mother as long as she can remember, that she has no other family that she knowns of.. it all paints a very troubling picture. She ends up passing out on their couch shortly after dinner, clearly exhausted and in need of a good rest, and Mallow tries to make her more comfortable by situating a pillow under her head and drawing a blanket over her. Dove and Mallow decide right then and there that there's no way this filly is going back to her mother, no matter what.

The next morning, Lavender insists that they head back to the spot where her mother left her. Surely she had to be worried sick about her now. Dove indulges the filly (what else could she do?), and the two spend the day waiting for the mare to return. And then the next day. Then the next. It takes about a week for Lavender to realize that her mother won't be returning. Dovekie comforts the sobbing filly, letting her know that she has a place with her and Mallow, if she wants it. Lavender doesn't even think twice.

Dovekie and Mallow adore their unexpected little filly, eventually naming Sea Lavender (which little Lavender is overjoyed at hearing). Lavender grows up with two loving mothers that are there with her every step of the way; when she attends her first ever day of school, when she fractures her horn playing buckball with other local children, when she discovers her special talent after planting and tending to a lavender bush in mallow's garden, when she loses countless writing contests but eventually takes second in the national M. Bluejay Fiction Authors of Tomorrow contest. They are with her through thick and thin.. though Lavender still can't help the occasional thought about her birth mother.

Lavender eventually leaves home, settling down in Canterlot to pursue a career in floristry. She works hard to make a name for herself and enjoys moderate success, becoming the favored florist of some Canterlot elite. The turning point of her career occurs when she's sought out to do arrangements for The Grand Galloping Gala. She is absolutely overjoyed (and in disblief) that she was even considered for such an important event, and puts her whole heart and soul into the floral arrangements for the gala.. and she catches the eye of one Prince Blueblood, who just so happened to be checking over the decorations for the gala.

Lavender doesn't know what to do or say (jeez, she's never been around royalty before..!), but luckily for her (or perhaps unluckily, she'll eventually find), Blueblood takes the lead and has the mare charmed beyond belief in seconds. Lavender leaps headfirst into a poorly conceived, and very secret, relationship with the prince. It's difficult to say she feels anything approaching love for the stallion.. certainly she was charmed by him at first, and it's so exciting to sneak around dating a prince.. but she feels little actual fondness for him.

And perhaps even worse, she's very aware of a certain fact about the stallion.. Blueblood is rich. He loved to buy her lavish gifts and take her on expensive dates, it was no secret that the prince had wealth beyond compare. Lavender may not have loved Blueblood, but she didn't want to give up the luxury of being his lover. Blueblood, meanwhile, was starting to get bored with the mare. She had seemed so interesting at first, but just like every other mare he dated, she grew positively boring - and Blueblood wasn't an idiot. He saw how much more the mare cared about his wealth than about him. It was high past time he moved on.

Lavender was left reeling after the relationship's sudden end. She had grown comfortable in the wealth Blueblood had showered on her, and worse yet, she discovered she was pregnant. Suddenly, Lavender was alone, and she was facing a challenge she wasn't sure she was prepared for. She threw herself back into her job, working tirelessly to avoid thinking about what was to come, until she was no longer in any condition to work.

Birdsong [pictured right] was born a shining beacon of his mother's past mistakes. Lavender tried her best not to see Blueblood in her son, but it proved too difficult. He had his eyes.

Lavender spent most of Birdsong's childhood paying more attention to her job than than to him. When Birdsong grew old enough to start questioning what happened to his other parents, Lavender made sure to shut any thoughts of that nonsense down quickly. Song grew up in a world that never cared to explain itself, and would more often than not just get scolded for bothering to ask, so he learned quickly to hold his tongue. He grows to be close friends with Snow Smokes and Moonshine Mirror, unaware of the relation between them.

Birdsong grows up to be quiet, nervous stallion, who finds trouble making new friends outside of his two childhood friends that stuck by his side. He works at Celestia's Royal Aviary in Canterlot, his talent being avian care and husbandry. He has a somewhat tense relationship with Prince Chaos Theory, who he insists should not be allowed near small animals.

One day, Snow Smokes will encourage Birdsong to seek out his birth father, leading him on a long journey that will end in Yakyakistan. Moonshine Mirror told him that it was possibly the most idiotic, dangerous idea Smokes had ever had. Birdsong will end up wishing he had listened to her.

WOOO THAT WAS A LOT UHHHH

tl;dr: the lady on the left is abandoned by her mom, gets adopted by a lesbian couple, grows up and moves to canterlot where she starts a relationship with prince blueblood, and ends up pregnant with colt on the right, who she becomes the sole parent of. yeesh even the tl;dr is long

it's not stated in the story, but dovekie song is a pegasus, and seashore mallow is an earth pony. they had a heck of a time figuring out how to raise a unicorn
also birdsong adores his grandmothers, because Of Course