Can you turn a one sink vanity into two sinks?

Yes, if there is enough room for 2 sinks. You will need to replace the counter top and piping.

If the vanity is wide enough you can remove the top and install a new one (or a reclaimed one if you were lucky to get your hands on one). You would have to cut two holes and install two sinks. It should be fairly easy to change the plumbing to accommodate both. You can get some countertops at a hardware store that are pre-cut to size, or make your own butcher block one. You may also want to keep an eye out on Facebook marketplace or Craig's list for people getting rid of old bathroom vanities. There are plenty of ways to spruce them up on this site. After all of this, if you choose to buy a new top, check the vanities at the store. Sometimes it is cheaper to buy an entire vanity.

This will give you some ideas. However, they look spendy so you might want to seek advice from a renovation company. I hope that helps.

https://www.google.com/search?q=turning+one+sink+vanity+into+two&rlz=1C1BLWB_enUS700US700&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiRssHZydnVAhXE4iYKHfhLA-8Q_AUICigB&biw=1024&bih=714

You can do this if you have the space, although it requires quite a bit of plumbing. You typically will have to add an additional drain, piping, etc. Definitely a job for an experienced plumber.

Maybe if your present counter top is long enough to add another sink without having to move the current sink. Check with your local plumber or handyman.

if your counter space is large enough to accommodate two sinks. Some additional plumbing will be needed.

If you have room under the counter for the plumbing and is your house has good water pressure and plenty of hot water, of course you can. My husband's and my sink are across from each other. If you ever get a chance for that, I recommend that. Our facing mirrors allow for 360* views, too. Best wishes 😇