The two brothers allegedly sold Musadikur Rohaman's BMW car, his wife's wedding dress and Â£1,200 worth of family gold to raise funds for him in Syria.
The two men, from Walsall, West Midlands, deny terrorism funding offences. Another two men, also appearing at the Old Bailey, deny funding offences.
All four say the money was to help Musadikur come back to the UK.
Prosecuting, Julian Christopher QC, said dry cleaners Mohammed Hussain, 26, and Mohamed Rohaman, 32, collected a total of Â£10,000 for their brother, a fighter in Raqqa.
Musadikur and his wife Zohura Siddeka, a teacher, both 27, left for Syria in December 2014.
"Musadikur had told people that he was going on holiday, but the true purpose for his trip was to go to Syria to join and fight for IS, and that is what he did," Mr Christopher said.
Mr Hussain also recruited family friends Mohammed Khan, 27 and Maruf Uddin, 26, both accountants, to help raise funds by taking out credit card loans and selling valuables, Mr Christopher said.
"This case concerns the steps which these four defendants took, in various different ways, to help Musadikur by sending money out to him, by selling items belonging to him and his wife, by obtaining a credit card and by extracting money from his and his wife's bank accounts."
A mother locked up valuables to stop two sons selling them to raise money for another son fighting for the so-called Islamic State, it is claimed.