Anonymous wrote:A man who has sisters is usually a better husband. Gender of the woman's siblings doesn't have nearly as big an impact.
-1
Depends on many factors: birth order is a consideration, and how they treated each other, if the parents were involved/absent/mentally ill, etc. Too many factors to count.
OP, there are wonderful only children and there are awful siblings - you just don't know until you meet the family and dig in a bit.
If your spouse has siblings, do those siblings celebrate what is good/happy/positive for your spouse, or do they want a piece of the pie? Just one example.