About travel to USA

Hi anil,
My hubby is in USA with h1b visa…visa is expiring on June 2022… We both( me and my kid) are staying in India… my doubt is can we travel untill June or should be there 6 months before expiration? Company will file extension on April 2022

You can travel any time as far as you have a valid visa (H4), passport valid beyond 6 months from the date of entry and primary H1B is in valid status at the time you enter the US.
You will need to carry copy of H1B I-797 approval notice (and receipt of the extension if extension is not approved before you travel), last three paystubs of H1B and other supporting documents as it applied to H4.