The broadcaster is believed to have seen off competition from rival bidders BT and Daily Mail & General Trust after offering £170m for the , according to reports.
ITV refused to comment on the deal, but Jeff Henry, chief executive of ITV's newly formed consumer division, said at a conference in Barcelona earlier this week that ITV was set to make a number of acquisitions as it attempts to beef up its online, mobile phone and interactive offering.
"ITV growth will also come from acquisitions and you can expect announcements imminently," he said.
ITV is actively seeking new revenue streams so it does not have to rely so heavily on TV advertising, which will come under increasing pressure from multichannel television when the analogue signal is switched off from 2008.
Personal video recorder ad-skipping technology, such as Sky+, is also adding to the dent in ITV's ad revenue stream.
As it stands, ITV1's net ad revenue accounts for 66% of the business, according to its latest results.
The broadcaster's plan is to make half its revenue from outside its core channel by 2012.
Friends Reunited was set up by London husband and wife team Steve and Julie Pankhurst in 2000. The deal will net the couple a rumoured windfall of £50m.
The business, which generated £4.6m last year, was put up for sale in the summer.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .