Solifenacin and Mirabegron do the same thing - reduce the tone of the bladder muscle (detrusor) to prevent bladder spsms (urgency). They can increase the chance of not fully emptying the bladder. It's a bit unusual to take both.
Tamsulosin makes you pee faster, and increases the chances of emptying the bladder, so you don't have to go so often. It's very fast acting, but only works for about 16 hours. If taken for a long time, it can shrink the prostate a bit too, which is useful if you have an enlarged prostate which is causing problems.
Finesteride is a half-way hormone therapy drug. It shrinks the prostate over about 6 months. It can also reverse male pattern baldness (although not if you've had it for years), and reduce growth of body hair acquired at puberty. There's no point taking it if he's on hormone therapy, because that does the same plus more.
As you haven't said what his urinary symptoms are, difficult to say how relevant the meds are. It would also be interesting to know his prostate size. Who prescribed them and what investigation was done in the process?