Can you connect 100 ah battery with a 130 ah battery?

It seems so. The only difference between the two is the amount of charge each holds.

Sure! But they should have the same voltages. In that case if you connect them in series then you sum up their voltages. however, if they are connected in parallel, you then sum up their flow rate currents(ah).

Example, if each is 12V, then connecting in series produces 24V. On the other hand, parallel gives 230 ah.