2 sets of twins

When Hikaru and Kaoru were little they thought they were the only ones in there little world. So they only trusted each other. But as they got older they had desires that needed attention so they would help one another out they liked it this way they didn't want anybody else to help with their sexual desires.

But what will they do when their mom takes in her friends twin daughters in for a year while she is away and they are the same age and all have to share a room.