I'm not sure if I'm understanding the ownership of Epic correctly, but from what I can gather it is a private company like Steam, so provided Tim was willing and Sony were prepared to, they could buy enough of Tim's shares to add to their existing percentage (probably an extra 46% at a value of $14.7 billion) to have the control stake in the company, which I assume would give them the same control/protection as owning the whole thing - just less of the profits.
Assuming that was achievable, I would then assume Sony could use their controlling stake in Epic to buy Bungie from Sony at cost, thereby lowering the Epic deal cost by $4billion and giving Tencent and Tim, etc a cut in profits from Bungie and an increased valuation of Epic at $36billion, and still potentially be in a situation that if Sony as a whole ever had enough to be able to afford the remaining 49% of Epic, they could use their controlling interest to take Epic public and do a hostile takeover with their controlling stake. Obviously not going to happen, but the first part would maybe be one way Sony could in effect buy Epic to use Fornite as a counterweight to CoD getting taken away and protect Unreal's success by protecting PlayStation.
Being a private company means that their owners (in this case as I remember Tim with slightly over 50% of the shares) decides if they sell or not and in the case they decide to sell, they also set the price.
But when some else buys shares or the whole company, they make an estimation of its value and set a price/percentage according to it on a way that both sides agree.
Tim has over 50% of the company, so even if others like Tencent or Sony have a big chunk of the company they can't take any big decision as would be to sell the company without Tim's approval.
If Sony (or Tencent) would want to buy Epic they should buy from Tim enough shares of the company to have over 50% of them to achieve a controlling stake. No need to include Bungie here, Sony just bought it so won't sell them or give it to anyone else.
I don't know what is the current percentage of Epic shares owned by Sony, but if they'd buy enough to control (so buy Epic) they wouldn't only pay that percentage of the value (let's say the 46%/$14.7 billion), on top of that they pay an extra on top due to several reasons, being one of them having several bidders wanting to pay for it.
That premium in recent big game company acquisitions ranged between 40% and 60%. Meaning that if what Sony would buy would be valued in $14.7B, they'd pay $22.05B if the premium is a 50%.
I think Sony wouldn't be interested on buying Epic because compared to what they already have that wouldn't provide them enough value. But if that would happen, I think it would be a Bungie-like situation: Sony would keep Epic under SIE reporting to Jimbo but selfpublishing as Epic as usual in all platforms including rival platforms and day one.
They would do it to add revenue and profit on top of what they already have plus to get more knowledge, tools, data and expertise and to ensure current and future Epic games will always continue being on Sony consoles and game subs. UE would continue to be provided to all gamedevs including Microsoft. Sony would rehash the Epic PC store turning it into their PSN PC store.
I think for Sony to pay well over 20B to own a majority (not all) of Epic would be too much for them and I think that in any case they don't have enough in their special cash budget dedicated for investments, acquisitions and Sony shares repurchases, since a big chunk of it isn't for gaming. If desired Sony could do different things like to pay with shares, or getting debt etc. but I don't see them doing that.
I think that instead Sony will keep investing on Epic buying shares in little chunks and who knows if maybe in 5 or 10 years from now they'll consider if they buy it or not, once Sony would have grown a lot and would have more than enough cash to buy it.
Tencent's expertise in GaaS is a reason why Epic partnered with them. Similar situation with Bungie except for being an acquisition rather than sell of shares.
In addition to this, Tentent also owns the main Chinese game stores, social networks and ads companies of China in both PC and mobile. And considering China is the top 1 country in gaming revenue and amount of players, it makes them a very appealing partner to help them enter China.
Tentent is also the company that makes more money with games in the world, meaning that they can provide all money they could need for any promising super ambitious project, aren't tied by money.
And well, Tencent also owns a ton of game and tech companies of all kinds so can provide them help with anything they may need. As an example: game server issues in games on a scale of Fornite are very different than the smaller ones. Tencent has other companies like Supercell with games that have a way bigger scale than Fortnite, so can teach Epic how they addressed these issues when they had them, offer them tech, data and knowledge, etc.