>>As a bilingual speaker myself I can attest to that. And as someone who has been passionately learning Spanish for 30 years, I listen and pay attention to others speaking it. What fascinates me a lot is a how the children of immigrant parents know both languages without any effort. I have two daughters who are adults, both born in USA. My wife and I speak with them only in English. Yet they both understand Russian very well; the older one even speak it (although with an accent and confusing gender and some grammar but yet better than most university professors of Russian language). And even though I speak to them in English, if necessary, I can throw some Russian words, barely pronouncing or articulating them. And they understand without an effort. For example, if we dine in a restaurant and I see someone at another table eating some crap, I can just comment about it, under my nose in Russian, and both daughters immediately grin and nod their heads. :)
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>The good thing about kids raised in a bilingual home is that they learn any other language very easily. At home we always spoke in Spanish to our daughter (in particular I did not want to ruin her life if she caught my terrible English pronunciation so I always made the effort of speaking in Spanish to my daughter) , and because she had a central american nanny when she was a baby, she would even distinguish both Spanish, and it was very funny hear her switching from Argentinean to central american accent when our central american friends were close. Now she reads and writes in English, Spanish, french and Japanese and wants to add Chinese and Italian.

Wow. Very impressive!