Thanks Tim ... I understand your response to my first question.  And I appreciate the clarity very much.    My brother has no children.   I have two children who will both test.   My mother is no longer living BUT she does have a sister who MAY be willing to test.   That should help.   And, I have her 1/2 brother testing as we speak.   So....I'll backdoor the phasing as best I can with a host of testing .... that works for me but is clearly impractical for most I'm quite certain .   On my second question I understand the single segment issue of IBS vs IBD.    But .... what about the situation re: IBS v. IBD where you and one other person share 14 matching segments ranging in size from 2.5 to 7.7 cM.    Now, any ONE of those segments ... maybe even 50% or more of those segments could be IBS .... but surely in a group of 14 seemingly matching segments ... even those coming in below the threshhold that causes us to all go .... "I don't think so" ..... there is a true IBD match.    Now ... we may not be able to find the connection via paper trail but doesn't such a complex match situation (multiple matching segments ... in my example 14) pretty much guarantee a biological IBD tie somewhere in that mixture?    Thanks for taking a second look at this. John ----- Original Message ----- From: "Tim Janzen" <[email protected]> To: [email protected] Sent: Saturday, January 7, 2012 12:00:13 PM Subject: Re: [AUTOSOMAL-DNA] SUBJECT: How do you work a 5 way FF        match        with        few clues ? Dear John,         If you have a two parent/one child trio and you phase the data you should be able to figure out about 83% of the mother's DNA.  If you have a two parent/two child quartet and you phase the data you should be able to figure out about 95% or more of the mother's DNA.  It becomes much more challenging when your mom's data isn't available for testing.  If your dad and you were both homozygous for a specific SNP (say AA and AA), then you would know that you got an A from your mom, but you wouldn't know what the other allele your mom had unless your brother got a different allele than you did, in which case you would know the two alleles that your mom had for that SNP.  If you have any children, I would suggest that you test your wife and your children.  This would allow you to phase your data.  You can then use your phased data to phase your dad's data.  If you have phased your data then you will have 50% of your mom's data and that portion will be phased.  If your brother has a!  ny children, I would also test your brother's children and his wife.  This would allow you to phase your brother's data.  You can then compare it to your dad's data which would in theory give you an additional 25% of your mom's data, raising the total of your mom's phased data to about 75% of what she had originally.         I am not sure that there is an easy answer to your 2nd question.  Simply having multiple people who match with you on a specific segment of DNA segment (say a 7 cM segment) doesn't necessarily imply that the segment is IBD.  If you have a child who also matches with these other people at that segment, then it is for all practical purposes IBD, but I could caution you not to jump to the conclusion that you have an IBD segment just simply because multiple people match you on that segment.  Also bear in mind that if you have multiple matches on a particular segment that some could be IBD and some could be IBS.  You can't really be sure which is which without phasing your data and then running the comparison. Sincerely, Tim Janzen