It doen't matter wheter they are a brother or a sister. It is about the love you have for them and the love they return.
If you truly want to know here are perfect combanations.
Boy+Girl - 1Yr difference between both of them.
Boy+Boy - 1yr difference between both of them.
Girl+Girl - 5yr difference between both of them.
Hope this sloves your problem!
Chat with our AI personalities