You can't just get an "okay" from a former group member to legally license a song for release.
The current ownership must be checked and contacted for clearance. Several companies in the last decade have "bought out" defunct catalogs and publishing entities, and are now forcefully going after those establishments who use a song under their ownership without proper licesning.
One of my side hustles before Covid wrecked things was freelancing copyright registration info. I was hired by a Los Angeles corporation to do the footwork in Washington DC, so I know how these types of "we wanna use song X from 1966 in our film or commercial" works.
Let's say, for example, you wanted to license "They Can't Hurt Me" by the Lyrics. Merely contacting the songwriter, Chris Gaylord, (who is no longer with us) or another former member of the Lyrics is insufficient as well as illegal in most cases. The original publisher, Bamboo Music, was purchased by the K-Tel corporation (yes, they are still around, one of the many outfits gobbling up orphan and dormat catalogs). So, K-Tel would have to contractually agree for the license. Good luck! I remember a planned project Bob Irwin asked me to kickstart when he still helmed Sundazed. I had pulled registrations for the songs and began to investigate if renewals were filed, and if not, the task of locating the original claimants or the current estate thereof. The project had to be canned when several tracks now owned by a corporate entity demanded a minimum sale of 25,000 copies!
Post your tracks here and I will check my archive. I've culled at least 95% of registration certificates originally filed for the songs in the "garage/"psych" genre. I can then check to see if any of these were renewed (believe it or not most of the 'classic' sides have indeed been renewed and are owned by a currently operating conglomerate).