The ability of your husband to adjust status in the US will depend on several factors.
If those factors are not in his favour then his option is to leave the US and seek immigrant visa in his US consulate in his country.
Unfortunately this will subject him to a bar on re-entry and based on the length of the period of his unlawful presence in the U.S.
One of such factors is but not limited to his ability to rely and benefit from on a previously filed petition by a family member or an employer on his behalf or a previously filed petition for his parents which list him as a child on the petition. It is not necessary for any of the petitions to have been approved, it could even have been denied, as long as it was"approvable when filed", he can rely on it. The important requirement is that it had to have been filed on or before 30 April 2001.
You are advised to contact an immigration lawyer to discuss the case and find a way forward.
You are welcome to use the link provided below.