Spying on my stepsister and my gf in the tub before to join them for a double blowjob

While I'm taking a shower before going out, my stepsister and my girlfriend walk into the bathroom and take a bath together right in front of me. They seem to have a lot of fun in the tub... they start kissing and touching each other in a very sensual way! It is impossible to resist the temptation to spy on them and even more so to masturbate while doing it! But I can't be satisfied with this and so I join them in the tub. The girls seemed to be waiting for nothing else and they start giving me a wonderful double blowjob after which I can only cum in their mouth