Moms: How old was your baby?

How old was your baby when he/she/they (multiples) could hold his/her/their head up on their own and not need mommy or daddy sitting right next to them while he/she/they were in the car seat for both short and long car rides?

My kids are 11yrs old (he will be 12yrs on July 14th in 2018) and 9yrs old (she will be turning 10yrs on Halloween night this month (2017) ).

So I need a bit of a refresher course, lol, before we succeed in TTC again.

Thank you in advance! ☺