Earlier quoted context omitted.
They are a family, as in, all of them were almost certainly created by the same group. Symantec said that Duqu is "near identical" to Stuxnet. As for Flame, Kaspersky[0] initially said that it contains no resemblance to Stuxnet, and then later on discovered that they've even shared a zero day in their early versions. From my understanding, I don't necessarily consider them as different software, more as a single soft…
Out of topic but your defense for referencing Kaspersky makes me wonder why people would see a problem with it? I'm not familiar with the field and don't know who's who.
People theorize they're controlled by the Russian government but I've never come across any evidence that they're anything other than a top tier security company though.
They have done some fairly bold moves in the past though, like cleverly calling out other AV companies that were copying their detections [0] and kind of embarrassing the NSA [1] when a NSA employee took their malware/cyber weapons home to their PC running Kaspersky AV, which detected the malware and sent it back to Kaspersky server for analysis.
[0]https://www.theregister.co.uk/2010/02/10/kaspersky_malware_d...
[1] https://www.bleepingcomputer.com/news/security/nsa-employee-...