I love my Mockingbird stroller and they have a dual seater stroller for newborn and an older infant/toddler. Different attachments too and it's cheaper than the Nuna but is very comparable. I also like that it's not too heavy as well.
Definitely Bob stroller
Hi, I recently switched to Cybex gazelle s2 and I love it, perfect for 2 under 2 I used to have nuna demi next and was super heavy and it was a pain to carry the extra seat