外國人會點樣叫佢地自己的仔女(大約廿歲)?

Westerners and Chinese are no different in terms of how they treat their kids (well, of course, there will always be exception). We Chinese like to think that our own kids will always be 'babies', 'sweeties' even when they are 20, 30, 40 or 70! The westerners usually also call their kids 'sweeites', 'babies', 'darlings' when they speak to others. Of course, if the parents don't care about their kids from day 1, then they won't even call them anything nice...
In formal writing and speaking, though, they would refer their kids as 'my children', less often as 'my kids'. 'Sweeties' etc. are only for casual speaking and usually only in front the kids. Eg. 'Sweetie, could you please help me with the rubbish?'; 'Darling, dinner is served.'
When talking to others:
'My children are my darlings.', 'These are my children, Paul and Marie.'
'My kids are really sweet, they gave me a card for my birthday!'
In writing:
'My sweet kids made me cake last weekend.'
In formal writing:
'My children, Paul and Marie, will take care of the family business from now on.'
Or even: 'Paul, my son; Marie, my daughter, will be the heirs to my business.'
Hope that helps!

I live in US, maybe I can help you. 大約廿歲 is an adult, and most parents just called their by their first name or honey. If the parents are talking to their friends will use my baby, my boy/girl, or their child's first name.
Sweetie / darling , ok? It really depends, I am a 13 years old, I don't like my mom called me sweetie/darlinig in public, most of the time she just called me by first name.

仔會叫--Guys,Young man, Son.
女會叫--Young lady, Honey, Sweetheart, Princess.


I hope this can help you with.