YOU SAID:

If I sit on him and he sits on me, we will sit on one another and on himself on me.

INTO JAPANESE

私が彼の上に座り、彼が私の上に座るならば、私たちはお互いの上にそして彼自身の上に私の上に座るでしょう。

BACK INTO ENGLISH

If I sit on him and he sits on me, we will sit on top of each other and on herself.

INTO JAPANESE

私が彼の上に座り、彼が私の上に座ると、私たちは互いの上にそして彼女自身の上に座るでしょう。

BACK INTO ENGLISH

When I sit on him and he sits on me, we will sit on top of each other and herself.

INTO JAPANESE

私が彼の上に座り、彼が私の上に座ると、私たちは互いの上にそして彼女自身の上に座るでしょう。

BACK INTO ENGLISH

When I sit on him and he sits on me, we will sit on top of each other and herself.