Ugh. Son wants a sibling

rell

Am dying deep down inside! My son is so lonely and although he's about to turn 7 and the age gap is real, he constantly tells my sister he wants a brother ( my sister just had a baby . But she already has twin boys) so most of the time he is over their house playing. . I want to tell him and my sister am trying. But it's not working and it's making me feel guilty. Plus my sister adds to the hype of him wanting a sibling . Ugh what to do what to do