Daddy's Dumb Question Time

TwinsDaddy

Note I'm looking for ballparks only, I'm aware there can be wide variations but apart from birth I'm really unclear about development.  So:

Many things are rated x lbs to y lbs.  When are they going to be 7 lbs?  20?  I have no idea how to quantify in my own head how long it will take for them to be at 9lbs, or 14, or whatever.

 Followup: we're having twins, I know the birth weight will be lower, but what's the catchup curve- like when will non-premie twins start matching singles in weight?

 Next question: how soon until their necks are developed?  how do you tell?  when is it OK to not support their head/neck constantly?  how do you tell?

OK, that was several but: last one for now; specific this time.  I've been to some baby sales and looked at a couple of dual bike trailers.  at what age and/or weight are they meant to be first used?  Should I be looking for a deal or will it be a dust collector for a year?

Wulfgar

From what I understand, when the twins are at their 40 week birth age they should be at "normal" baby weights then track like normal.  As for when they hit 20# etc it all depends on genetics our almost 2 year old is hanging at 36# and is in size 5

LuckyDad

TwinsDaddy:

 Next question: how soon until their necks are developed?  how do you tell?  when is it OK to n

LittleFish1

Female lurker here; my daughter was starting to hold her head up at 2.5 weeks however it still needed some support when she'd be lifted from horizontal position. At 2 months she was even better at self supporting her neck.

Weight wise, my da

Coltsdad

All of the size/weight questions are mostly genetic.  My cousin had twins about 6 weeks before our son was born and the girl is roughly the same height, but a little lighter than our son, but her brother is smaller than both of them... he may be a