Des anyone think that Mark has stronger feelings for Callie being আরো just best friends?

Ugh..No,not really.
আপনি can see that he loves Lexie. Callie&Mark are just friends,best friends.It looks like after sex that they had,when AZ was in Africa,all Mallie অনুরাগী started to think they're in love.Sex doesn't mean that suddenly he loves her অথবা that she loves him.