Here is the entire Dash Family!

Rainbow Dash (Daughter of Bow and Windy, adopted big sister of Scootaloo, granddaughter of Firefly and Flash, niece of Blaze and Sunshower, cousin of Barley and Pickle and owner of Tank)

Scootaloo (Daughter of Snap Shutter and Mane Allgood, niece of Aunt Holiday and Lofty, ancestor of Sable Spirit, adopted daughter of Bow and Windy, adopted little sister of Rainbow, adopted granddaughter of Firefly and Flash, adopted niece of Blaze and Sunshower and adopted cousin of Barley and Pickle)

Bow Hothoof (Husband of Windy, father of Rainbow, adopted father of Scootaloo, son-in-law to Firefly, son of Flash, brother to Blaze, brother-in-law to Sunshower and uncle to Barley and Pickle)

Windy Whistles (Wife of Bow, mother of Rainbow, adopted mother of Scootaloo, daughter of Firefly, daughter-in-law to Flash, sister-in-law to Blaze and Sunshower and aunt to Barley and Pickle)

Firefly (Mother of Windy, mother-in-law to Bow, Blaze and Sunshower, grandmother of Rainbow, Barley and Pickle and adopted grandmother of Scootaloo)

Rainbow Blaze (Brother of Bow, brother-in-law to Windy, son of Flash, son-in-law to Firefly, husband of Sunshower, father of Barley and Pickle, uncle of Rainbow and adopted uncle of Scootaloo)

Rainbow Flash (Mother of Bow and Blaze, mother-in-law to Windy and Sunshower, grandmother of Rainbow, Barley and Pickle and adopted grandmother of Scootaloo)

Sunshower Raindrops (Wife of Blaze, sister-in-law to Bow and Windy, daughter-in-law to Firefly and Blaze, mother of Barley and Pickle, aunt of Rainbow and adopted aunt to Scootaloo)

Barley Barrel (Twin sister of Pickle, daughter of Blaze and Sunshower, niece of Bow and Windy, granddaughter of Firefly and Flash, cousin of Rainbow and adopted cousin of Scootaloo)

Pickle Barrel (Twin brother of Barley, son of Blaze and Sunshower, nephew of Bow and Windy, grandson of Firefly and Flash, cousin of Rainbow and adopted cousin of Scootaloo)

Snap Shutter (Husband of Mane, father of Scootaloo, sister of Holiday, sister-in-law to Lofty and ancestor of Sable Spirt-Deceased)

Mane Allgood (Wife of Snap, mother of Scootaloo, sister-in-law to Holiday and Lofty and ancestor of Sable Spirit-Deceased)

Aunt Holiday (Sister of Snap, wife of Lofty, sister-in-law of Mane, aunt of Scootaloo and ancestor of Sable Spirit-Deceased)

Aunt Lofty (Wife of Holiday, sister-in-law of Snap and Mane, auntie of Scootaloo and ancestor of Sable Spirit-Deceased)

Sable Spirit (Ancestor of Snap, Mane, Holiday, Lofty and Scootaloo-Deceased)

Tank (Pet of Rainbow Dash-Deceased)

Headcanon:

The events of Season 8-9 (With the exception of The Washouts and Best Gift Ever) and Rainbow Roadtrip are not canon.

Barley and Pickle Barrel are the children of Sunshower Raindrops and Rainbow Blaze.

Scootaloo gets adopted get Bow Hothoof and Windy Whistles after her original parents and two aunts pass away.

Sable Spirit is an ancestor of Scootaloo.

Tank dying is based on this: https://youtu.be/9SbTxbBT7-I?si=X6szZ_sBi30q4jVI