Richard is Locke's biological father in my understanding.

Emily was dating a man twice her age, (Richard would fit). Richard was at the hospital and Emily's mother was reluctant to say he WAS NOT the father. Locke was put up for adoption.

Richard had to find John. Richard was convinced that John was his 'the one.'.. (so Matrixy). We're led to believe the man that Sawyer killed was John's father ... maybe he swindled John just like he swindled everyone else. HE NEVER said he was JOHN'S father!.. He only said, "You needed a father and I needed a kidney".. never acknowledge completely that he was the father of John... (unless I missed something). .. and I'm sure I may have.

John packed over 600 knives?.. (remember the knife was the error in Richards test).. so Locke has EVERY knife he can find-or trying to prove WHO he is to ..??????? the man who rejected him/.. Richard.

I believe that Richard is John's bio-dad. And I'm still not convinced that Jack/Claire's dad is Jacob.. (even though we're suppose to believe that based on tonight's episode).

Where does that lead? I dunno.