This is how close they are
This is straight down from Charles Lister, the Saudi-paid advocate for Syria's radical Islamist rebels. The high council of Ahrar al-Sham which is the biggest rebel organisation in Syria held a vote on whether to merge with Jabhat Fateh al-Sham which is al-Qaeda's Syria franchize and another large rebel organisation.
The vote failed, the two will not be merging, but this is really besides the point. Even a failed vote shows once again how close the rest of the Islamist rebellion is to al-Qaeda. So close that its largest component will realistically contemplated an outright merger.
In September when Russia and the US concluded the illfated Kerry-Lavrov deal on Syria Russia suggested treating Ahrar al-Sham as a terrorist organisation alongside JFS (previously al-Nusra) but Americans refused.