What Should I Feed A New Kitten?

ok so i got 2 kittens. one is a female and the other is a male. i am planning on getting another cat (male). they are about 4 weeks old now. im just trying to figure out what they should be eating first before introducing them to eachother. does everyone feed their babies kitten milk? or do you let them drink regular milk for awhile then switch them over? oh ya, the male has black spots on him like he was born that way