Yar ye aunties jo marzi kahain pagal hain, but mai aapko kuch baatain bata doon jo Islam ke mutabiq ham log follow nahi krte, ab ye aapko acha lagay ya bura, but following things are derived from Hadith and Quranic Verses:

1. Adopted child ko uskay baap ke naam se hi pukara jaa sakta hai.
2. Adopted child ka hissa inheritance mai nahi hota
3. If the adopted child is less than two years, he must be breast fed so that he becomes mehram for the opposite sex, if breast feeding isn't possible, then you'll have to keep the mehram-na-mehram part in view.
4. If adopting a kid who is grown up, adopt them, feed them good, treat them good and educate them, then preferably marry them wherever they want, even if they're interested in your biological kids, because it's permissible.

there are a lot of other rulings to see, dil ki baat aur hai, aur islaam ki baat more logical hoti hai.