if one of mine gets sick a lot, and gets weak, i get the doctor. there's usually an infection.

do you have to pay for the doctors visit for both people then?

yes, you put the stethescope on one, and then you get the diagnonis.

If it says "a bit sick" I just move them around until I get a diagnosis for free. If it says that the person is weak, that's when I buy a doctor's consultation.

You are just treating the symptoms, but not necessarily the illness. If a peep is sick regularly, even if it seems to be cleared up each time by a pill or other medicine, the likelihood is that they have a grave or serious illness that will need a doctor's consultation to diagnose. They will not necessarily show as "weak" until the illness has become more serious.

Sorry, I wasn't clear in my post.

As far as I know, both peeps may be in need of a baby boost. Doctor's consult tells that if they need it or not. Beginning from my 2nd gens I began buying it for both of my peeps at the start of the new generation.

However, I don't think it is a necessity. In my first gens I didn't buy doctor's consult (didn't have enough money, and also I didn't know he would advice about that subject), and had 6 kids in each of them. Much later a peep got ill in one of the families, and after visiting the doctor I learned that the guy needed some baby boost. Then I bought one for his wife and she also needed baby boost (but they had 4 or 5 kids at that time). This was a couple which had several unsuccesfull attempts before each kid. So in later generations, I took this habit of visiting the doctor at the beginning.

Still, I think it is also possible to inject each peep a dose of baby boost, and forget about the doctor. As I understand, even if your peep doesn't need it, using won't give any harm.