No it's not, it must be a blockchain not a blockgraph, if two blocks share the same parent then only one of them can be in the chain, and because blocks can't be 'editted' without simply remining them, you have to choose either one chain or the other. Even if you could, do that, there's a host of other issues like the same coins being spent on both chains, or the block height in the coinbase being wrong

In bitcoin each block in the chain contains a reference to one single parent block (except the very first block which has no parent block) thus this is not possible as would require a reference to two parent blocks.