Would / have you let someone else breastfeed your bub? Or have you breastfeed a friend/relative s baby?

I am trying to work out how i feel about this. I have spoken to some older women who were breastfeeding in the 70s who would feed other mum's (close friends) kids when babysitting and the baby needed a feed.

I am not immediately comfortable with the idea, but it also doesn't freak me out.

Would it make a difference if it was your sister vs a friend or sister in law (non relation)?

Would it make a difference if it was another woman s breastmilk, but given via cup or bottle rather than from the breast?