Haley has only 2 sisters ?/:)O.o

Okay so we all know Taylor and Quinn.When Lydia (their mom)comes to them in season 7 she says something like 'ah my 3 favorite daughters' so that lets us believe she has only 3 daughters cause parents (real parents) adore all their sons/daughters equally.In season 2 episode episode 11 when Taylor arrives she says:'Wow Haley didn't mess around.You are Nathan right ?'N:'Yeah , do I know you ?'T:'Well you should I am your sister in law?'N:Vivian ?'T:'Don't make me smack you!'N:Quinn ?'T:'Taylor' [...]
So that means there are 4 ? and if they are four why Lydia said when she came to them in season 7 : My three favorite daughters and also in season 1 Nathan told her when he was at home and Haley was reading or corecting something a test he said like : Wow you have a lot of relatives or you have a big family :D something like this.