I got a double stroller, although they are about 21 months apart, it's useful especially when we go out and big one want to sleep, and i train small one to sit and sleep there too. Carry small one whole day tend to be tired easily if your big one also want you.
As for rocker is your big one still using? For nap ? If not 1 is enough. Can try to teach her to share too.
Is ur big one still sleeping in cot? Perhaps it's time to upgrade to bed?
Find a ways that you are more comfortable with.
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