Thank you so much Fabio. you are absolutely right. but as per I know TDT is for nuclear families and DFAM is also for multiple families not single multigeneration family. I am dealing with precisely one single multigeneration family and thats why got confused with several application PLINK, whether --assoc application should be apply or not? whether --fisher can be applied for this case or not? and most precisely I want to ask about the imputation application of PLINK.

Can we impute the seq data or array data for the same? actually, I have whole genome snp array data as well as whole exome sequencing data for large multigeneration family and was trying to do the imputation since long time, but never able to do it successfully. then I extend my search and find that there is population data usually use in the imputation application of PLINK, thus again I got confused about the application of PLINK for single family.