I don’t know how old they are per se, but they are older.
http://www.mangago.me/read-manga/a_thousand_cranes/
http://www.mangago.me/read-manga/mr_100_perfect/
http://www.mangago.me/read-manga/behind_the_desk/?2AgU
http://www.mangago.me/read-manga/kamisama_no_uroko/ (I recommend all this authors works btw, but read the XXX series before therapy game)
http://www.mangago.me/read-manga/namaiki_kareshi/
http://www.mangago.me/read-manga/toshishita_kareshi_ni_hirowaremashita/?3UwG
I've got the perfect list: http://www.mangago.me/home/mangalist/995603/
Goes from roughly oldest to younger pairings
any mangas where the ukes or both of the couples are in 30s