Should it be on first come, first serve basis?

Loving somebody or doing something for somebody or accepting something
from somebody should it be on first come first serve basis? For
instance, a girl had her birthday and her parents and her boyfriend
both had planned a surprise for her but the boy had to give up for
that moment because the girl had to be with her parents and postponed
the surprise till she is done celebrating it with her family. (just
watched this serial in it such was the situation) and I was wondering,
what may come but family is always the first priority but that was
because the girl didn't knew that her boyfriend had a surprise for
her. So she was happy with her family but had she known about his
plans for her still probably she would have been with the family but
only half heartedly, I feel. Would it be fair then? Why it always
becomes so, that if you have to choose between the two family comes
first? No, I don't have any problem untill it's that they are still
completely with them from mind and body but if you are just with them
for being self then the priority which you are giving is all fake,
isn't it? It's just that you are supposed to hence you are. Given a
choice probably you would have been with both but mostly it's not
possible. Even in todays generation expecting this is too much from
your fate! So choice is to be made and it always goes by default. Uff!
All these dilemma's of life!
But can a person make choice between their spouse and parents, between
their children and spouse. If there is conflict then whom you are
supposed to chose? What should be the basis? Can love be weighted on
time basis or should it be on feelings basis? Can you say that the one
who came first are the one who need to be supported or the one who had
just came but then your love for them is equally intense and hence
they should get the vote? (considering that there is no right or wrong
situation but gap between thoughts. That you can't say that one is
right and other is wrong probably both are right and wrong at their
place!) what will you do then?