Now what I have speculated and theorized that I believe to be canon is that Apocalypse recreates or clones his body from the Techno Organic cells with in Cables Blood. Hence Apocalypse Clone body to some extent is formed from Summers DNA or Genes. This would also make Clan Akkaba Descendants of Apocalypse and at least a portion of them also descendants of Cable and the summers family
How this all happens and comes to be is quite complicated so here is
Brief part of a brief Description of Cable and Deadpool #26 from Uncannyxmen.net
Thousands of years ago, a young Cable – then called the Traveler – kills Apocalypse – then simply called En Sabah Nur – in combat. Apocalypse’s followers, the Dark Riders, now wish to follow the Traveler, but he’s not interested in taking En Saban Nur’s place and tells Nur’s chronicler, Ozymandias, that being the most fit to survive means that you should help those who are less fortunate. As he watches the Traveler leave, Ozymandias mingles En Sabah Nur’s blood with the Traveler’s.
I believe the answers to this is in Peter Milligans Blood of Apocalypse story line Running from X-men Vol.2 182 - 187 and Fabian Nicieza Prequel to Blood of Apocalypse in Cable in Deadpool 26-27 and also X-force Vol.1 #37 which are the key issues In which I believe makes my theory more then speculation and part of Marvel canon.
Issue summaries for Cable & Deadpool 26-27 from www.Uncannyxmen.net
Now here are some scan from that issue
cable wounded in a fight
Apocalypse died fighting Cable but Ozymandias mixed both there blood together to bring him back to life cloning a new body from that mixture
the scans below explain about the blood and cloning
and here are some wiki links on how the blood and Techno Organic Virus works.
It was believed that this strain of techno-organic virus was either created by Apocalypse or discovered by Apocalypse on board the Ship. This virus was actually created by Mister Sinister as a means of killing Apocalypse. This attempt failed due to Apocalypse's immense powers, and the virus fell into Apocalypse's hands. Apocalypse later used the virus to infect the infant Cable. The virus has many similarities to the Transmode Virus and the two may be closely related. Techno-organic matter of this kind usually appears as blue/grey metal.
This strain of virus is less virulent than its counterpart, needing blood contact to transmit, and usually taking a longer time to infect a person, although it can have sudden short bursts of activity, during which spikes of techno-organic matter form from the diseased body and the body's parts change their forms. Another difference with the Transmode Virus is that infection is very painful and can incapacitate a person.
Humans infected with this virus receive increased strength and the ability to directly interface with machinery. While infected material can change its shape, it is unknown whether a fully infected person is capable of shapeshifting (Apocalypse can, but he already had this power before being infected).
Apocalypse was introduced to the virus from a young Nathan Summers, calling himself the Traveler. In a battle between Traveler and Apocalypse, they were both cut and Ozymandias, Apocalypse's servant, had Apocalypse's body returned to the newly found Celestial Ship, that Apocalypse, at that time, could not understand or communicate with. With Traveler's blood mixed with the Techno-Organic Virus and his own, Apocalypse was healed in a chamber of the ship and, infected with the virus, could then understood the ship. Years later, Apocalypse used the virus to infect Nathan Christopher Charles Summers as an infant, leading to his transport to the future and his growing up to be Cable. It was possible that Apocalypse used this knowledge of past/future events to infect infant Nathan Summers so that he himself would become Apocalypse in the past.
please take note when it say With Traveler's blood mixed with the Techno-Organic Virus and his own.
so when ever Apocalypse makes a new body its from cables blood the techno-organic virus and his own.
In cable and Deadpool #5 september 2004
Cable absorbs Deadpool’s liquified mass in order to cleanse himself of the facade virus, as a side-effect he becomes genetically bonded to Deadpool.. So Deadpool isnt a summers but he does carry the summers dna in him now.
Tigra’s child William is not Pym’s son but the Skrull who was Impersonating Pym on a Genetic level technically making Pym the genetic father.