Subject: First born genetic contribution?

One of my professors mentioned something about the first born child leaving 
behind a small amount of cells that attack and insert their genetic patterns into  
all fertilized eggs that occur afterwards.  Thus, your younger siblings would 
have more in common with you than your parents?  Is this true?  What more can you 
tell me about this?

If it is true, what about the case of a woman giving birth to two children from 
different fathers?  Would the second resulting child have genetic materials from 
the mother, the father, and the previous father via. first born child?

Re: First born genetic contribution?