There are two avoidances, that I train myself to take, when it comes to mingling with Christians or those claiming to be Christians. This is regardless of family members or non-relatives. By default, I give the benefit of the doubt, when someone proclaims himself/herself Christian.
- When most topics of interest are not of the spiritual kind, not related to God at all. These are those who talk about jobs, science and technologies, vacations, news, weather, stocks, etc. These generally have their hearts set on something else besides the Lord and His Kingdom and I should take care to avoid them. They seek self-fulfillment, not God. God is their excuse to Heaven.
- When most topics of interest are of the spiritual kind, always vainly, legalistically or shallowly praising God. God is their excuse to Heaven.
So what then, is true fellowship? It's the discussion of all topics that naturally grounds in the Creator. I said naturally, so it's not a ritually intended one as many fundamentalists do. The more zeal one is truly for His Kingdom, the more evangelical one will be come. So the more one loves to speak of the bible, theology, and yet there's no increase of boldness or desire to bring the Gospel to the gentiles, the more obvious this person has become avoidance #2 that I listed above.
Last but not least, think evangelical to problem #1. As they are most likely open to the Gospel, whether they claim themselves to be Christians or not. They are humbler. For #2, I have no answer other than ignoring them if possible. They are no likely to be truly humble and won't admit their pride. Perhaps lead them by example is best, and be watchful of them should they think they are/want to be part involved in your examples/projects.