This isn't part of the main story it's just a long note on how I came to decide which ponies are members of Babs Seed's Family. Partially to explain my choices and partially in the hope that others will use this as fan-canon in their written works.
When I first saw the Apple Family Reunion and examined the Group Photo I saw several things.
Mainly the mare and stallion behind Babs and Apple Rose. Since, even in large family group photos, members of immediate family tend to stick close to each other I decided they could be Babs' family. My reasoning is:
The Mare: Apple Dumpling, shares Bab's hair colours
The Stallion: who apparently is named Red Hickory (although I personally prefer his fan name of Buckwheat - Bucky for short.) has a similar coat colour to Babs, has the same eyes and the same freckles.
And since Babs has an older sister I chose Pink Lady as she was the closest pony to the others I had proclaimed Babs' family.
And, although it won't feature beyond hints in conversation I even found myself thinking up a fictional biography for them. 
Apple Dumpling - Manehattanite through and through. She is a member of the Apple family by blood. Related to the Orange family as a cousin two or three times removed. While Applejack calls her Aunt, she isn't really. She is the daughter of Apple Rose, who is Granny Smith's cousin. Although, no one knows for sure if AJ and Dumpling remember that. AJ's been calling Apple Dumpling "Aunt" for so long that's how their relationship has developed. She's an honorary aunt even if she isn't a biological one.
She owns and works in a diner in Manehatten which sells all kinds of things but specialises in Apple based treats. Her speciality is Apple Fritters.
One day she met: 
Red Hickory- which is his official name, I quadruple checked this on google, fan forums, mlp wiki and imdb. The voice artist who did his one line is credited to the character "Red Hickory" along with a picture of the pony.
Now a member of the Apple Family after marrying Apple Dumpling his Cutie Mark of a baked apple is an interesting coincidence. Working as a hired-hoof on an Apple family farm he was sent to Manehatten to make a delivery to Apple Dumpling's new diner. The two hit it off right away and after a whirlwind romance were married.
Knowing his new wife wanted to make a serious go at her diner he left the farm and went to work in the city - getting a job as a grounds-keeper in Manehatten Central Park. He's head's grounds-keeper now and has grown to like the city his wife and family were born in. But he will always be a farm pony at heart.
Knowing that Babs had an older sister I chose the mare closest to the family group, which was:
Pink Lady - The firstborn daughter who a little over a year after Dumpling and Red were married. Big sister to Babs. While Manehatten in accent and temperament she takes a little after her father in her love of outdoors and wide open spaces.
Around the same age as Applejack, give or take a year, she fully intends to go into her mothers buisness one day but, for now, she's going through a gap-year travelling phase. She has a long term rental on an airship:
Which she flies around Equestria, sometimes paying her way by picking up passengers. And giving the occasional ride to Apple family members when they want to get to a reunion in a hurry.
She travels with friends - who are unseen in the picture above because they weren't family members and, as such, wouldn't be going to the reunion.
Mostly she travels to visit other members of the Apple Family, working on their farms and orchards, gathering together the various family recipes for Apple treats, along with an occasional adventure.
Babs. We all know and love. She has her mothers hair and her fathers eyes and freckles along with a similar coat colour. She had a fondness of the outdoors but takes after her mother and mostly loves the city.