Dealing specifically with England and Wales:
Is it possible for there to be more joint tenants in equity for a specific property than the number of joint tenants in law?
For example, if A, B, C contribute to the purchase of a property, is it possible for only two of these parties to be legal joint tenants, whilst all three parties are beneficial joint tenants?
Yes. It is fairly common for there to be one owner at law, but another person who has a beneficial interest - such as a long-term cohabiting partner. This may arise because the parties set it up that way, or perhaps more often when courts find that there is a "constructive trust" or a "resulting trust". See for example the concurring opinion of Lord Hope of Craighead in Stack v Dowden [2007] UKHL 17,
Parties are, of course, free to enter into whatever bargain they wish and, so long as it is clearly expressed and can be proved, the court will give effect to it. But for the rest the state of the legal title will determine the right starting point. The onus is then on the party who contends that the beneficial interests are divided between them otherwise than as the title shows to demonstrate this on the facts.
The resulting court process may find that the beneficial interest exists, or not, and what fraction of the property it represents. It's common to find situations where one party put up most or all of the whole purchase price of a house, which was then registered in both names, and they then disagree about whether it should be split 50-50 or otherwise - that's an example of the beneficial ownership differing in proportion from the (equal) legal ownership. (See Jones v Kernott [2011] UKSC 53 at paragraph 51 for an explanation of this particular pattern.)
The same sort of case arises when a cohabiting partner does not own the house, but still contributes to the mortgage and other bills - then, depending on the facts at hand, there may be a "constructive trust", and the partner is entitled to a share of the sale price of the house even though they are not its legal owner. A "resulting trust" might arise when someone contributed money for the purchase of the property, even though they didn't end up as a registered owner, but the parties acted in other respects as if they were joint owners.
The answer to your question is Yes.
