can we switch student visa to dependant visa in the UK?

Answer 1

Yes you can. If you marry someone, or have a child, then this person can stay as a dependants visa.
If your currently here in the UK as a student and you get married, then as long as either you or your wife is still a full time student, then you can switch to a dependant visa.

This is at the discretion of the immigration officer or home office. In most cases, you are allowed.

Answer 2

So, as advised by Mr Curious, get breeding!