Coincidently (adverb)
Simultaneously; at the same time
Coincidentally (adverb)
In a coincidental manner.
Wiktionary
Coincidentally (adverb)
in a way that results from chance despite being very unlikely
“the three are coincidentally reunited when captured by the enemy”
“her dad coincidentally happens to be the accountant at the bank”
Coincidentally (adverb)
at the same time
“the report should be published coincidentally with the letter”
Oxford Dictionary