When son was approx 25 lbs he was prescribed ranitidine 15mg/ml at 2 mls twice daily. He now weighs 32 lbs. Is the dosage the same?

Depends. You are right in thinking that since he has increased his weight, his medication should also be increased since pediatric medicines are dosed based on weight. To roughly stay the same, you could give him 2.5 ml twice daily. If it is hard to measure out 2.5 ml, you could safely give him 3 ml twice daily. Sometimes doctors will keep the dose the same, and if the lower dose works as well, that is ok.