Navamsa says about spouse from lagna to 12th everything says about spouse .
if you say ketu in 6th aries means he is scorpio asc . for scorpio ketu is co ruler of lagna so he has all the qulaities of mars as lagnathipathi as well as 6th house matters . he is robust , sound health , broad shoulders , short temper , slender physique . masuline body (assuming jupiter is not influencing lagna )
ketu in 6th is very good over all success no enemies , no debts etc etc . person has superiority complex since he has high level of courage . has weird apetite . his maternal uncle suffers . aries rules head so he may have head realed issues he acts without thinking . he will go first if fight happens anywhere . angry person . hot blood but all these depends much on mars , above said will come full if mars is placed well else reverse happens .
venus mars combination makes the person playboy . upto the level of spoiling their health . it also goes under the name kuja dosh . creates problems in married life , this combination is only good for sex life and not for marriage . relationship with sisters and aunt will also suffers .
if this combination occured in kendra or kona its nice but not in 8th house
forgot to mention . for scorp asc mars 6th lord in 8th goes in the name called vibreetha raja yoga sudden change in life after marriage . everything is nice except married life both of the partners indulges in sexual adventures , it will not happen if jupiter aspects 8th house ...