Many Danish records are on
http://www.sa.dk/ao/ (not name-indexed, but if you find a date/parish from other records you can check it here)
beta.familysearch.org shows Johan Martin Wensch m. Cathrine Marie Muller 23 Apr 1795 in Budofi (parish), Aalborg.
Several baptisms to them are listed, all in Budolfi (note that these children are indexed with surname "Johansen") - there are two entries for a Hanna Petrea, one in 1800 one in 1802 (first daughter died, perhaps?)
And possibly that he remarried 05 Nov 1806 to Ife Birgithe Dessen (Skaeve, Hjorring) (one child for them listed in 1807, in Fladstrand).
The images relating to these records can be found on the Danish site I linked at top: the remarriage in 1806 (opslag/page 161 of the Skaeve records) does I think show Johan as "Chirugus" although it's very curly/difficult handwriting.
I think of the siblings, Frederiche possibly married a Jens Henrich Hansen, there are children for them listed on the familysearch beta in Odense.
http://ddd.dda.dk/nygaard/visning_billed.asp?id=401650&sort=e - not exactly sure but this might be indicating he passed away in 1811?
http://ddd.dda.dk/nygaard/visning_billed.asp?id=77101&sort=e - and this for his second wife in 1820?
