Any yaoi with age gap uke is older seme is younger

http://www.mangago.me/read-manga/yami_ni_tooboe_mune_ni_toge/
http://www.mangago.me/read-manga/ren_ai_nenrei/
http://www.mangago.me/read-manga/alluring_sentiment/
http://www.mangago.me/read-manga/hada_no_ue_no_renai_jijou/
http://www.mangago.me/read-manga/renai_tsuu/
http://www.mangago.me/read-manga/fingertip_s_love/
On any of these manga you will see a older Uke younger seme tag.

http://www.mangago.me/people/tag/2337/Oyaji+Uke/