i was invovled with a man who had 2 teens and we got along great.... i even got along with his ex wife. but i think it is all about understanding...
my father on the other hand was a step dad... my sisters were very young when my parents met, and when they eventually married, my dad wanted to adopt them. my sisters refused, and would say the "you're not my father" shit... their real father never saw them...and gave no support whatsoever. after my father died (they were mid teens) ... they felt really guilty for the things they did and said to him... and now consider him to be their father. so much so that when their bio dad died, they told their bio grandmother "my father died 8yrs ago... i dont know the man you are talking of".
however, not everyone erases the lines of "half" and "step". BOTH my grandmothers were married 3 times, and so we have lots of both in our family. My poor sister has actually been told by my mom's side that she doesnt "really" belong because our mom's dad was different from our aunts' dad. and the same sister was told by my dad's mom (who was actually her best friend and they spoke every day for years and years) "you know, your' not my real granddaughter, but i love our conversations" some peole may look at that as endearing --- like in a movie and cry "oh you accept me and dont have to".... but my sis was 7 when my dad and mom got married.... she THOUGHT and FELT like a REAL granddaughter... and therefore bringin it up when she was 50 was just quite upsetting--- made her feel alienated and different, not accepted