Thanks in advance for the help. I'm wanting to add a new lavatory to my bathroom upstairs. I hope i can explain my situation well enough in words.

The existing toilet drain is about 4 feet from it's 3 inch waste vent. The new lavatory I want to add is about 6-8 inches away from the vertical section of the 3 inch waste vent for the toilet. Is it okay just to add a sanitary Tee into the waste vent and add my new lavatory drain there? Will creating this wet vent be an issue?

Or, is it a better idea to run a separate vent line off of the new lavatory and then tie into the waste vent higher and run a separate drain for the lavatory and tie in with a Wye connector near the toilet drain.