SOLVED. Romance 90s book where heroine is adopted and hero is representing birth family asking for medical help

[Indus]

hi! I've been looking for this book for years so hoping someone can help. It's likely from the 90s- heroine is a professional and has been raised by a couple she considers her parents, not looking for her birth parents. However, the hero comes to her and says he's her stepbrother in her birth family, and they are looking for her for medical reasons- her sister is in the hospital and she can help her.
Spoilers


She doesn't want to meet her birth mother because her adoptive mother is going to be upset. She had a brother who was taken back by his birth parents. But it all ends well with her marrying her stepbrother and her mothers having a good relationship

[Indus]

The book is lifeline by Sarah temple- found on another site!