Yes, other sim families do age as you play your other game saves. Unless you have aging turned off in the options. No the family wouldn't be the same as you last saved them, due to having aging on.
If you are sharing a computer it may be worth turning off aging.
Here's a quote from Dellena and aging options below:
The only way to stop that if you have the families all in one game is to turning aging off entirely. Otherwise, I'd have a separate game for each family so they don't age while you're not playing that game. If you want the families to all be friends, then your only option is to turn aging off.
Aging OptionsClick image to see larger view:
When you go into your saved game go to top right and the Options Menu>Game options>Gameplay tab.
There you will see the aging options:
Auto Age (Played Sims) with 3 choices in a drop down menu of:
No / Yes / Only Active Household
Auto Age (Unplayed Sims) with a check box.
If you want all the sims, including the ones you play, to
not age up choose 'No' and make sure the check box next to Auto Age (Unplayed Sims) is unchecked.
If you want just your family you are currently playing to age up then click 'Only Active Household'.
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Reference Links:
Multiple personalized families
http://www.carls-sims-4-guide.com/forum/index.php/topic,25425.0.html