Filed I-130 for both parents, only receive one receipt

[newbee]

Hi,

I filled 2 separate I-130 for my dad and mom. However, I only got one receipt back.

Now I regret a lot that I didn't put the 2 application into one envelope. Somehow I had the impression that I must file them separetely.

Is there any way I can combine the 2 application together so that they'll get green cards the same time?

Thank you very much!

Newbee