Fragile X mental retardation protein (FMRP) is an RNA binding protein necessary for correct spatiotemporal control of neuronal gene expression in humans. Lack of functional FMRP causes fragile X mental retardation, which is the most common inherited neurodevelopmental disorder in humans. In a previous study, we described the biochemical and biophysical aggregation properties of constructs spanning the conserved region of FMRP and of two other human fragile X related (FXR) proteins, FXR1P and FXR2P. Here, we show that the same regions have an intrinsic tendency to aggregate and spontaneously misfold towards β‐rich structures, also under non‐destabilizing conditions. These findings pave the way to future studies of the mechanism of formation of FXR‐containing ribonucleoprotein granules and suggest a possible link with the as yet poorly understood FXR proteins’ associated pathologies.Structured digital abstract  FXR2P binds to FXR2P by fluorescence technology (View interaction)  FMRP binds to FMRP by electron microscopy (View interaction)  FXR1P binds to FXR1P by electron microscopy (View interaction)