Suggestions for multi purpose lens.

Hi! I'm interested in a few suggestions on a multi purpose lens which are kind of opposite either other.

Right now I have a sont a7r ii

I'm into photography of my kids (portraits) and birding.

I've always wanted to purchase a nice lens for portraits but they are extremely expensive for a nice one on a one income household.

But now my wife and I have two possible uses (portraits+birding) that it may be worth finding one we could do both decently with.

I'm aware I probably need a 400mm minimum for birding.

Wondering if anyone has any recommendations?

Budget $500-1500.

Looking for a good quality lens. Not a stock lens.

Thanks for any input!