A man may be secluded with his mother and reside with her; with his daughter and reside with her; with his sister but he may not reside with her and he may sleep with them without clothing.

Beraisa (R. Chalafta ben Shaul): A daughter may sleep with her father (without clothing) until the age of 3; a son with his mother until the age of 9.

From this age, each must sleep with their own covering.

Beraisa: If two men were sleeping in one bed, each covers himself with his own covering and recites the Shema. If the other person was his own child, it is permitted (since he will not have inappropriate thoughts).

In Bavel they say that for a man and wife, he is permitted to recite the Shema if he faces away from her (even without being separated by a covering. Since he is used to her, he will not have inappropriate thoughts.)

R. Yaakov bar Acha citing R. Elazar: However, here we are unsure about a man and wife, whether for the recital of Shema there is no need for a covering to separate them since they are considered the same body. The Gemara does not answer this question.