An updated forkcoins tree chart (only blockchains)
As far as I'm aware, the newest graph mapping forkcoins which spun off from Bitcoin is Bitcoin Magazine's Map of Bitcoin forks infographic. It was published in April 2019, so it will not include newer forks like the upcoming BCH split. It does include the major project forks, but doesn't list all forks (there have been over 40 mostly irrelevant forkcoins).
I looked up a prior project called Map of Coins which was aiming to collect the full pedigree of altcoins that forked from Bitcoin's codebase (and other original projects) but it appears to not have gotten updated since 2017.