2 sentences

1. 这是他们的家务事，外人不好插手。

   zhè shì tā​men de jiā​wù​shì, wài​rén bù hǎo chā​shǒu.

   This is their private family matter; it's not appropriate for outsiders to interfere.

   Source: Dong Chinese Dictionary

2. 既然这是他们两人的家务事，你就不要插手了。

   jì​rán zhè shì tā​men liǎng rén de jiā​wù​shì, nǐ jiù bù yào chā​shǒu le.

   Since this is their private domestic affair, you shouldn't interfere.

   Source: Dong Chinese Dictionary