I have sponsored my brothers this year. One brother's family got a Visa. Now, another brother needs an Affidavit of Support or Joint Sponsor. So, when I will able to give another Affidavit of support/Joint Sponsor to my brother or someone?

After how long I will be able to give him another Affidavit of support/Joint Sponsor to my brother or someone? (For example, 8 months, 1 year, 2 years etc.)

As far as I remember, (I haven't gonne through that in a while), ther is no limit how many Affidavits you can sign in a moth, year, life-time. It depends on your income, as all the persons you already sponsored (brother's family) are now counted... in other words: you have to make enough for your family, your brother1's family and brother2's family.