This century alone, the pair have either enjoyed or endured a number of the same players - enough, in fact, to form a semi-competent XI (and without having to include Warren Feeney).
Would the following names get in your combined side?
Bywater had two spells in South Wales, both on loan and with seven years in between. Just months after the latter, he made the temporary switch to Hillsborough, where he helped the Owls to promotion from League One. A permanent deal followed, but his placed was seized by Chris Kirkland and he left for Millwall in 2013.
Plucked from League Two Wycombe by Cardiff - ahead of rivals Swansea City, no less - Johnson was eventually sold to Birmingham City for £5 million. Successive relegations with the Blues and Wolverhampton Wanderers followed, before the defender reunited with ex-Bluebirds boss Dave Jones at Wednesday for a three-month loan spell, during which Jones was relieved of his duties.
Cardiff's much-loved former captain left for Hillsborough in 2009, having been denied a shot at the play-offs on that very ground in his final game for the Bluebirds. Purse was instantly appointed skipper by new boss Brian Laws, a move which caused some disharmony among the squad, but couldn't recapture his previous form and had his contract terminated by mutual consent with the Owls struggling in League One 18 months later.
Impressive in South Wales, the former Feyenoord defender was signed by Scottish giants Celtic in 2008. Five years on and without a club, Jones arranged for Loovens to join him, Johnson, and various others at Wednesday - only to be sacked before the Dutchman's international clearance came through. Three years on, Loovens is the Owls' club captain.
Having impressed on loan at Hillsborough last season - despite being restricted to just four appearances for Carlos Carvalhal's side - Bennett was all set for a permanent return but for the intervention of Aston Villa owner Tony Xia. Instead, he ended up in Cardiff, making his long-awaited debut on Friday.
One of Jones' signings at Wolves, Olofinjana followed his old boss to both of his future clubs on loan. The Nigerian returned to Wednesday on a short-term basis in 2013 but left shortly after.
The Irishman helped Cardiff back to Division One in 2003, but was signed by Wigan 18 months later - en route to the Latics' promotion to the top flight. Wednesday took him on loan during the 2007-08 campaign, in which he helped the Owls escape relegation.
Signed from Barnsley in 2006, McPhail lost in FA Cup, play-off and League Cup finals with the Bluebirds, before returning to South Yorkshire with Wednesday under, you guessed it, Dave Jones. By then his legs had pretty much gone and he left shortly after Olofinjana, with Stuart Gray preferring to play Kieran Lee in central midfield.
Three strong seasons at Cardiff - in which he scored 45 goals - prompted Bothroyd's return to Premier League football with QPR in 2011. A year later, however, he was back in the Championship on loan to Jones' Owls, where he spent much of his time on the right of a front three. As far as Wednesdayites are concerned, that did not excuse the striker's lack of effort and no tears were shed on his return to Loftus Road.
A promotion hero with Wednesday in 2005, MacLean's departure to Cardiff at the end of his contract two years later left the Owls fans stunned. Things didn't work out at Ninian Park, however, and the Scot was sold to Plymouth Argyle after just six months - reuniting with his old boss Paul Sturrock.
MacLean's strike partner for seven games during Wednesday's 04-05 campaign, the Trinidadian returned to Southampton with as many goals at the end of his loan. After spells at Sunderland and Stoke City, Jones joined Cardiff midway through their season in the Premier League and stayed for two years - scoring on 19 occasions.
Bennett in action for Brighton against Jones and Cardiff