Dash’s family is quite misfortunate in a sense.  
She never intended to have kids as soon as she did, not to mention the way that she did.
 
During a wonderbolts tour after party she found herself getting drugged by a mysterious stallion at the bar. He then proceeded to lead her out of the building and raped her. The day after she woke up, dazed, on a stray cloud. Rainbow tried to deny it ever happened and did her best to move on, yet months later she got a harsh reminder when she found out that she was pregnant. The father she later realized was none other than Wind Rider, looking to extract some type of psychotic revenge for getting him kicked out of the wonderbolts and practically stealing his fame.
 
Rainbow kept the baby. She hoped that things would have perhaps gotten a bit of a happy ending.  
She hated being pregnant and had second thoughts constantly during her pregnancy. It was the worst 11 months of her life, but her friends where luckily there to help her through it.
 
When she was Silver Lining she got a lesser heart attack. She looked a lot like her dad. Something that Rainbow hadn’t really expected for some reason.  
She tried to be a good mom yet she was always reminded of that horrid experience when she saw her and so she often acted stiff and awkward around her.  
Rainbow tried to hide as much as possible in her job and seldom had time to play with her daughter.
 
Silver however wanted to spend as much time as possible with her mom. She was her big idol and rolemodel, and she wanted to be just like her. She desperately seeks her mothers approval. Rainbow just kinda feels guilty for being a bad mom yet don’t really know what to do and how to act around her daughter.
 
Silver wants nothing more than to become a wonderbolt just like her mom, but unfortunately she isn’t as skilled at flying and often ends up just injuring herself when trying to perform dangerous stunts.
 
Some years after Silver was born Rainbow Dash ended up having a night of passion with Discord of all ponies, and yet again found herself pregnant. This time she knew sooner and came running to Discord begging him to help her do SOMETHING! She just couldn’t handle going through another pregnancy and having another child. Discord, having lost a son before and had no wish to lose another child (planned or not) “overtook” her pregnancy and vanished. He never told Rainbow that he kept the child, only retreated back to his chaos dimension.  
This resulted in a draconequus hybrid named Haywire.
 
Haywire grew up away from pony culture, yet was always fascinated by it and ultimately went there in a pony disguise. She doesn’t know who her mother is nor that she has any siblings.